Demand curve, in economics, a graphic representation of the relationship between product price and the quantity of the product demanded. Such conditions include the number of consumers in the market, consumer tastes or preferences, prices of substitute goods, consumer price expectations, and personal income.

The term supply refers to how much of a certain product, item, commodity, or service suppliers are willing to make available at a particular price. Demand refers to how much of that product, item, commodity, or service consumers are willing and able to purchase at a particular price.

Supply curve, in economics, graphic representation of the relationship between product price and quantity of product that a seller is willing and able to supply. Product price is measured on the vertical axis of the graph and quantity of product supplied on the horizontal axis.

The demand curve is downward sloping, indicating the negative relationship between the price of a product and the quantity demanded. For normal goods, a change in price will be reflected as a move along the demand curve while a non-price change will result in a shift of the demand curve.

Demand curves are used to determine the relationship between price and quantity, and follow the law of demand, which states that the quantity demanded will decrease as the price increases.

Factors That Affect Supply & Demand

• Price Fluctuations. Price fluctuations are a strong factor affecting supply and demand.
• Income and Credit. Changes in income level and credit availability can affect supply and demand in a major way.
• Availability of Alternatives or Competition.
• Trends.
• Commercial Advertising.
• Seasons.

Demand Force Along Curve Demand forces can cause us to move up and down the demand curve. Remember, we are talking about moving along an existing curve, not shifting the curve. This movement happens when the price of the product rises and falls. If the price were to fall, we would be moving down the demand curve.